Fortnite features the things called Times Missions that offer bonus rewards. Those include defenders, survivors, perk resources, evolution materials, schematics, heroes, experience, Transform Keys or V-bucks. Each bonus reward of Time Mission is able to be claimed once on completion. You need to know that Timed Missions are marked on the map with a clock sign and the missions rotate every 24 hours.
There are a few kinds of Timed Missions but only Mini Boss missions are able to reward V-Bucks. Mini Boss missions are also called as Mini Boss Alerts or just Mission Alerts. You are able to view the current Mini Boss Mission Alerts in Fortnite above.
The currency of Fortnite called V-Bucks as a Mini Boss mission reward is quite common and not possible as regular mission rewards. According to Free The V-Bucks, the rewards are 25 to 40 V-Bucks on a single mission and the missions change once every day. Please keep in mind that completing the same mission again will not grant you the bonus reward. The other kinds of Timed Missions such as Storm missions are only able to reward evolution materials as the bonus reward. As for the Elemental Storm missions, they reward elemental resources for their respective elements. Aside from that, events have also featured their own kinds of Timed Missions.
How to unlock the new areas and Timed Missions in Fortnite? Progressing the main questline will eventually unlock the new areas with more missions to play. Apparently, each Storm Shield Defense on the questline will reveal more mission spots on that area. You start the game from Stonewood and have to complete the questline of 34 quests in order to unlock Plankerton. You will earn access to Canny Valley after completing Plankerton questline. Twines Peaks is the final area you unlock. Every area is significantly harder than the last one and more quests are needed for the next area. For those who are curious about High V-Bucks rewards, they are more often found from harder areas. In addition to the new mission spots, you will also unlock some different kinds of missions, materials, and daily quests as you progress.
On top of the page you are able top see the current Mini Boss Mission Alerts such as the rewards without launching the game, fetched directly from Save the World servers each 15 minutes. It does not matter where the V-Bucks reward mission is, there will be a lot of people completing it for the free V-Bucks.
For your information, the amount of Mission Alerts available past Stonewood was doubled to six and Mini Bosses were added to all of them in patch v2.3. This thing makes the name switched to Mini Boss Mission Alerts, patch v3.4 refocused Mini Boss Mission Alerts towards Transform Keys and high rarity items and removed crafting ingredients from the list of the reward. Those changes seem to raise the amount of the the V-Bucks mission reward from 15-30 to 25-40 V-Bucks. After the patch v3.5 Mini Boss Mission Bucks Alerts are no longer able to be selected in Stonewood and Plankerton if you have not unlocked the mission alert is attached to but you are still able to access it with the higher level party.